A 2-cyanoacrylate is generally produced by condensation of a cyanoacetate and formaldehyde in an organic solvent, followed by depolymerization of the polymer thus obtained at high temperature and reduced pressure. A crude 2-cyanoacrylate obtained here generally has low purity, poor adhesion performance, poor stability, etc., and it is therefore further distilled to give a purified 2-cyanoacrylate.
With regard to distillation and purification of a 2-cyanoacrylate, a method is known in which, in order to prevent polymerization of the 2-cyanoacrylate, an anionic polymerization inhibitor such as diphosphorus pentoxide, phosphoric acid, or paratoluenesulfonic acid, and a radical polymerization inhibitor such as hydroquinone, catechol, or pyrogallol are added to a crude 2-cyanoacrylate, which is then subjected to distillation at reduced pressure while heating.
Furthermore, JP-A-1-135754 (JP-A denotes a Japanese unexamined patent application publication) proposes a method in which distillation is carried out while continuously and countercurrently adding a polymerization inhibitor from an upper part of a distillation column.
Moreover, U.S. Pat. No. 2,794,788 discloses a method in which distillation is carried out under a flow of an acidic gas such as SO2, BF3, HF, or CO2, for the purpose of inhibiting polymerization of a 2-cyanoacrylate in a distillate system.
Furthermore, JP-A-4-124168 proposes a method in which distillation is carried out without using the above-mentioned acidic gas but instead using a polymerization inhibitor such as a BF3 ether complex salt or a BF3 carboxylic acid complex salt.